Electron gun evaporation apparatus and film formation method using the electron gun evaporation apparatus

ABSTRACT

An electron gun evaporation apparatus capable of efficiently using an evaporation source includes an electron beam position controller which determines, as an applicable range, a range within which the distribution of the film thickness growth rate is almost constant in each scanning direction of an electron beam to be applied to an evaporation source in a crucible for the irradiation position of the electron beam, on the basis of information pertaining to the electron beam irradiation position and the film thickness growth rate in the electron beam irradiation position.

TECHNICAL FIELD

The present invention relates to an electron gun evaporation apparatuswhich forms a metal film and the like on a semiconductor wafer andelectronic part substrate by using an electron gun. The presentinvention particularly relates to an electron gun evaporation apparatusincluding an electron beam position controller for controlling andlimiting the application range of an electron beam to be applied to anevaporation source in a crucible in order to increase the use efficiencyof the evaporation source, and a film formation method using theelectron gun evaporation apparatus.

BACKGROUND ART

Electron gun evaporation apparatuses are extensively used in variousfields of industries as apparatuses for forming films on the surfaces ofobjects. Especially in the manufacture of various electronic parts suchas a magnetic head and magnetic disk, electron gun evaporationapparatuses are often used to form various conductive films andinsulating films.

An outline of the arrangement of a conventional electron gun evaporationapparatus will be explained below with reference to FIG. 4.

An electron gun 6 comprising an electron beam generator 61, electron gunscanning coil 62, and crucible 63 is placed in the lower portion of avacuum chamber 1 that can be evacuated. The apparatus also includes afilm thickness controller 13 for detecting and controlling the filmthickness growth rate of a film formed on a substrate 3 placed in thevacuum chamber 1. The apparatus further comprises an electron gun powersupply 10 for supplying a high voltage to the electron beam generator61, a filament controller 11 for controlling the filament power of theelectron beam generator 61, a sweep controller (SWEEP controller) 12 forcontrolling the position of an electron beam that impinges on anevaporation source 7 in the crucible by supplying a direct current tothe electron gun scanning coil 62, and an apparatus controller 14 forcontrolling the electron gun apparatus.

The filament controller 11 installed outside the vacuum chamber 1supplies electric power to the filament of the electron beam generator61, thereby turning on the filament. The filament controller 11 suppliesa high negative DC voltage (−6 to −10 kV) to the electron beam generator61 to generate an electron beam.

An evacuating means 2 evacuates the vacuum chamber 1 to a vacuum degreeof 1.0E-4 to 1.0E-6 Pa. A substrate holder 4 on which the substrate 3 isplaced is installed in the upper portion of the vacuum chamber 1, and afilm thickness sensor 5 for monitoring the film thickness is installedbelow the substrate holder 4. The film thickness controller 13 isconnected to the film thickness sensor 5. The film thickness controller13 can detect the film thickness growth rate of a film formed on thesubstrate 3 on the basis of that film thickness of the film formed onthe substrate 3 which is measured by the film thickness sensor 5.

The electron beam generator 61 of the electron gun 6 generates anelectron beam by receiving the high negative DC voltage (−6 to −10 kV)supplied from the electron gun power supply 10. The electron gunscanning coil 62 deflects the electron beam generated by the electronbeam generator 61 through about 180°, and controls the electron beamirradiation position. The crucible 63 is a receiver for the evaporationsource 7 for film formation. The crucible 63 itself is cooled by acooling mechanism.

The process of forming a film on the substrate 3 placed on the substrateholder 4 by using the conventional electron gun evaporation apparatushaving the above arrangement will be explained below.

While the interior of the vacuum chamber 1 is at the atmosphericpressure, the substrate 3 is placed on the substrate holder 4, and theevaporation source 7 is supplied to the crucible 63. When thesepreparations are completed, the vacuum chamber 1 is closed, and theevacuating means 2 evacuates the vacuum chamber 1 (until the vacuumdegree reaches 1.0E-4 Pa). When this evacuation is completed, coolingwater is supplied to the cooling mechanism for cooling the crucible 63,and the electron gun power supply 10 is operated to apply a set negativeDC voltage. The applied voltage is −6 to −10 kV.

When the high voltage is completely set, a predetermined emissioncurrent value is set by monitoring an emission current meter. The valueof the emission current increases in proportion to the electric powerapplied to the filament. When the emission current flows, the electronbeam generator 61 applies an electron beam to the evaporation source 7in the crucible 63, and this electron beam heats the evaporation source7. The electric power of this electron beam is the product of theapplied voltage and emission current of the electron beam generator 61.

Generally, if the electron gun applied voltage is 6 kV and the emissioncurrent is 1 A when evaporating an Al material, the electron beam poweris 6 kW. When the electron beam impinges on the evaporation source 7after that, the evaporation source 7 is heated to a high temperature andstarts evaporating, and an evaporated film adheres to the substrate 3placed on the substrate holder 4. When a predetermined film thicknesshas adhered to the substrate 3, the power supply to the filament isstopped, so the emission current becomes zero.

When the emission current becomes zero, the power of the electron beamalso becomes zero, so the application of the electron beam to theevaporation source 7 stops.

The film thickness sensor 5 measures the film thickness on the substrate3. On the basis of the measurement result from the film thickness sensor5, the film thickness controller 13 connected to the film thicknesssensor 5 calculates the film thickness growth rate during filmformation, and calculates a film formation time required to obtain apredetermined film thickness by using the following equation, therebymanaging the film formation time. By thus managing the film formationtime, the film thickness controller 13 controls film formation forforming the predetermined film thickness on the substrate 3.

(Film thickness of substrate 3)/(film thickness growth rate)=filmformation time

When the film having the predetermined film thickness is completelyformed, the application of the voltage is stopped by stopping theelectron gun power supply 10, thereby completing the film formationprocess.

In some conventional electron gun evaporation apparatuses, however, theevaporation source supplied into the crucible does not uniformly andevenly reduce because the electron beam spot of the electron gun, thatis, the irradiation position of the electron beam is fixed.

To make the reduction of the evaporation source uniform and even,therefore, a method of averagely evaporating the evaporation source byscanning the electron beam irradiation position in the X- and Y-axisdirections has been proposed (patent reference 1).

Patent reference 1: Japanese Patent Laid-Open No. 11-200018

DISCLOSURE OF INVENTION Problems that the Invention is to Solve

Unfortunately, the evaporation source in the crucible does not uniformlyevaporate in accordance with the electron beam irradiation position.

FIG. 2 is a view schematically showing the relationship between theelectron beam irradiation position in the X-axis direction on theevaporation source in the crucible and the film thickness growth rate onthe substrate. A and B in FIG. 2 indicate examples of the loci of sweepwhen the electron beam irradiation position is changed in the Y-axisdirection. FIG. 2 shows that the distribution of the film thicknessgrowth rate when the irradiation position is changed in the X-axisdirection on the evaporation source in the crucible includes a portion ain which the film thickness growth rate evenly distributes from thecenter to the edge of the crucible in the radial direction, and aportion b in which the film thickness growth rate abruptly decreases atthe edge of the crucible in the radial direction. This tendencysimilarly applies to the locus of sweep in the Y-axis directionperpendicular to the X-axis.

The film growth rate decreases in the portion b because the crucible ismade of a copper material having a high thermal conductivity, andchannels through which cooling water flows are formed inside thecrucible and the crucible itself is always cooled to a low temperature.Even when the electron beam impinges on the crucible itself for a shorttime (a few seconds), therefore, the evaporation source does notevaporate from the crucible, so the film thickness growth ratesignificantly decreases.

In the conventional method of averagely evaporating the evaporationsource by scanning the conventional electron beam irradiation positionin the X- and Y-axis directions in order to avoid the difference betweenthe film thickness growth rates in the electron beam irradiationpositions as described above, the widths of scanning of the electronbeam irradiation position in the X- and Y-axis directions are set withina narrow range by taking account of safety so as not to extend theirradiation position to the crucible outside the evaporation source.

Accordingly, only a portion near the center of the evaporation source isused, and the evaporation source must be replaced although the edgeclose to the inner wall of the crucible is not used up. That is, theevaporation source must be replaced when 30% to 40% of the whole amountis used, and this decreases the use efficiency of the evaporationsource. Especially when using an expensive material such as gold orsilver as the evaporation source, a low use efficiency of theevaporation source is a large economical burden.

The present invention has been made in consideration of the aboveproblems, and has as its object to provide an evaporation techniquecapable of applying an electron beam over a broad range to anevaporation source placed in a crucible, thereby increasing the useefficiency of the evaporation source.

Means of Solving the Problems

To achieve the above object, an electron gun evaporation apparatusaccording to the present invention is an electron gun evaporationapparatus including, in a vacuum chamber configured to be evacuated, anelectron gun which generates an electron beam by accelerating thermionsgenerated from a filament by applying a voltage to the thermions, a filmthickness controller which detects a film thickness growth rate of anevaporated film formed on a substrate by applying the electron beam toan evaporation source and evaporating the evaporation source by heat,and a sweep controller which controls an irradiation position of theelectron beam on the evaporation source, comprising electron beamposition control means for acquiring information concerning anirradiation position of the electron beam from the sweep controller, andinformation concerning a film thickness growth rate corresponding to theirradiation position from the film thickness controller, determining anapplicable range within which the electron beam can be applied to theevaporation source, and storing the applicable range.

Also, a film formation method using an electron gun evaporationapparatus is a film formation method using an electron gun evaporationapparatus including, in a vacuum chamber configured to be evacuated, anelectron gun which generates an electron beam by accelerating thermionsgenerated from a filament by applying a voltage to the thermions, a filmthickness controller which detects a film thickness growth rate of anevaporated film formed on a substrate by applying the electron beam toan evaporation source and evaporating the evaporation source by heat,and a sweep controller which controls an irradiation position of theelectron beam on the evaporation source, the film formation method usingthe electron gun evaporation apparatus comprises an acquisition step ofacquiring information concerning an irradiation position of the electronbeam from the sweep controller, and information concerning a filmthickness growth rate corresponding to the irradiation position from thefilm thickness controller, an electron beam position control step ofdetermining an applicable range within which the electron beam can beapplied to the evaporation source, on the basis of the informationconcerning an irradiation position of the electron beam, and theinformation concerning a film thickness growth rate corresponding to theirradiation position, and storing the applicable range in a memory, andan evaporation step of depositing an evaporated film on the substrate byapplying the electron beam to the evaporation source and evaporating theevaporation source by heat, within the applicable range determined inthe electron beam position control step.

EFFECT OF THE INVENTION

According to the present invention, it is possible to apply an electronbeam over a broad range to an evaporation source placed in a crucible,thereby increasing the use efficiency of the evaporation source.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1 is a view showing an outline of the arrangement of an electrongun evaporation apparatus according to an embodiment of the presentinvention;

FIG. 2 is a view showing an example of the relationship between theX-axis sweep and film thickness growth rate of the electron gunevaporation apparatus;

FIG. 3 is a flowchart for explaining the procedure of the process ofdetermining the application range of an electron beam to be applied toan evaporation source, on the basis of the relationships between thescanning positions in the X and Y directions and the corresponding filmthickness growth rates; and

FIG. 4 is a view showing an outline of the arrangement of a conventionalelectron gun evaporation apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the present invention will be exemplarilyexplained in detail below with reference to the accompanying drawings.Note that constituent elements described in this embodiment are merelyexamples, and the technical scope of the present invention is defined bythe scope of the appended claims and is not limited by the followingindividual embodiment.

FIG. 1 is a view showing an outline of the arrangement of an electrongun evaporation apparatus of the present invention. In the followingexplanation, the same reference numerals as in the conventional electrongun evaporation apparatus explained with reference to FIG. 4 denote thesame constituent elements, and a repetitive explanation will be omitted.

First, during the installation or periodical maintenance of the electrongun evaporation apparatus, an electron gun controller 15 functioning asan electron beam position control means presets a sweepable use range(the application range of an electron beam to be applied to anevaporation source) as follows.

The sweepable use range can be determined by operating a sweepcontroller 12, film thickness controller 13, and film thickness sensor5. For example, the sweep controller 12 controls the electron beamirradiation position in the X- and Y-axis directions, and the filmthickness controller 13 monitors the film thickness growth rate in eachirradiation position, and detects the film thickness growth rate in theinternal plane of a crucible 63. On the basis of the measurementresults, the electron gun controller 15 determines the sweepable userange.

FIG. 3 is a flowchart for explaining the procedure of the process ofdetermining the range (applicable range) within which the electron beamto be applied to the evaporation source can be applied, on the basis ofthe relationships between the scanning positions in the X and Ydirections and the corresponding film thickness growth rates.

In step S301, the range and number of measurement points of anevaporation source 7 in the crucible 63 are set in an apparatuscontroller 14 as the electron beam application range (sweep range).

In step S302, the sweep controller 12 sets the irradiation position in aposition (sweep start position) where electron beam application isstarted.

In step S303, the sweep controller 12 makes preparations to enableelectron beam application, and sets the output of an electron beam to beemitted by an electron beam generator 61 at a fixed value. The sweepcontroller 12 applies a high voltage to the electron beam generator 61.After that, a filament power is input, and an emission current issupplied, thereby supplying a predetermined electron beam power. At thesame time, the film thickness sensor 5 and film thickness controller 13are operated and made enable to monitor the film thickness growth rate.

In step S304, the electron beam generator 61 starts outputting anelectron beam under the control of the sweep controller 12.

In step S305, the film thickness controller 13 measures the filmthickness growth rate on the basis of the measurement result from thefilm thickness sensor 5.

In step S306, the electron gun controller 15 acquires informationconcerning the electron beam irradiation position from the sweepcontroller 12, and information concerning the film thickness growth ratecorresponding to the electron beam irradiation position from the filmthickness controller 13, and stores these pieces of information in amemory of the electron gun controller 15 (an acquisition step).

In step S307, the sweep controller 12 determines whether a predeterminedtime has elapsed from the start of electron beam emission. If thepredetermined time has not elapsed (NO in S307), the sweep controller 12returns the process to step S304, and repeats the same processing. Onthe other hand, if it is determined in step S307 that the predeterminedtime has elapsed, the sweep controller 12 advances the process to stepS308.

In step S308, the electron beam generator 61 stops outputting theelectron beam under the control of the sweep controller 12. In stepS309, the apparatus controller 14 determines whether the measurement iscompletely performed in all the measurement points within the set sweeprange. If not all the measurements are completed in the sweep range setin step S301 (NO in S309), the apparatus controller 14 advances theprocess to step S310.

In step S310, the sweep controller 12 changes the electron beamirradiation position to the next irradiation position, and repeats theprocessing from step S303.

The electron gun controller 15 acquires the irradiation position (X-axisirradiation position) in the X-axis direction output from the sweepcontroller 12 and the film thickness growth rate information in theX-axis irradiation position monitored by the film thickness controller13, and stores these pieces of information in the internal memory of theelectron gun controller 15. Then, the sweep controller 12 controls theelectron beam emitted from the electron beam generator 61 in the Y-axisdirection, and the film thickness controller 13 monitors the filmthickness growth rate in the irradiation position (Y-axis irradiationposition) in the Y-axis direction by the film thickness controller 13.The electron gun controller 15 acquires the Y-axis irradiation positionoutput from the sweep controller 12 and the film thickness growth rateinformation in the Y-axis irradiation position monitored by the filmthickness controller 13, and stores these pieces of information in theinternal memory of the electron gun controller 15.

In step S309, the apparatus controller 14 terminates the process if allthe measurements within the entire sweep range set in step S301 arecompleted (YES in S309).

On the basis of the film thickness growth rates corresponding to the X-and Y-axis irradiation positions and stored in the memory, the electrongun controller 15 determines the range within which the distribution ofthe film thickness growth rate is almost constant in each scanningdirection of the electron beam as the range (applicable range) withinwhich the electron beam can be applied (an electron beam positioncontrol step). For example, the electron gun controller 15 determinesthe application range in the X and Y directions within which the filmthickness growth rate corresponding to the portion a shown in FIG. 2 hasan almost constant distribution. In this determination, the electron guncontroller 15 can determine the application range of the film thicknessgrowth rate within a predetermined reference range as the applicationrange that gives an almost constant film thickness growth ratedistribution, by comparing the film thickness growth rate in eachirradiation position in the X- and Y-axis directions with the referencerange.

By performing the above operation, the electron beam sweepable use rangebased on the film thickness growth rate, that is, the application rangeof the electron beam to be applied to the evaporation source isdetermined, and stored in the memory of the electron gun controller 15.

Also, the electron beam scanning position and the film thickness growthrate on the substrate are such that the film thickness growth rates inthe electron beam irradiation positions stored in the electron guncontroller 15 are equal for the same evaporation process (e.g., thematerial and shape of the crucible and the material of the evaporationsource). Therefore, even when the evaporation process is changed to anevaporation process different in, for example, the material of thecrucible and the type and capacity of the evaporation source, theelectron beam application range (sweepable use range) can be determinedfor a different kind of evaporation source if information pertaining tothe corresponding film thickness growth rate is stored. Accordingly, theevaporation source can be used at high efficiency of use.

This obviates the need to limit the scanning widths (application range)of the electron beam spot in the X- and Y-axis directions to a narrowrange by taking safety into account, unlike in the conventionalapparatus. Therefore, it is possible to apply the electron beam over awide range to the evaporation source 7, and increase the efficiency ofuse of the evaporation source 7 from 30% to 40% as the conventionalvalue to 70% to 80%.

The electron gun controller 15 is connected to the apparatus controller14 that performs various settings required for the operation of theelectron gun evaporation apparatus, for example, the setting of the highvoltage of the electron beam generator 61, and the settings of thefilament power, emission current, and electron beam sweep range. Whenactually operating the electron gun evaporation apparatus (FIG. 1)according to the embodiment of the present invention, the apparatuscontroller 14 presets the high voltage value, filament power or emissioncurrent value, and electron beam application range (sweep range) as inthe conventional electron gun evaporation apparatus described withreference to FIG. 4. In this case, the electron gun controller 15compares the sweep range preset by the apparatus controller 14 with theapplicable range stored in the memory of the electron gun controller 15.

If the set value of the sweep range set by the apparatus controller 14has exceeded the electron beam applicable range stored in the memory ofthe electron gun controller 15 in step S301 of FIG. 3, the electron guncontroller 15 controls electron beam application so as not to exceed theapplicable range, and performs answerback to notify the apparatuscontroller 14 that the set value has exceeded the applicable range.

The electron gun controller 15 incorporates an alarm (not shown), andcan generate an alarm sound by the alarm if the irradiation position ofthe electron beam to be applied to the evaporation source 7 in thecrucible 63 has exceeded the value of the sweepable use range. It isalso possible to separate the alarm from the electron gun controller 15,and allow the apparatus controller 14 to receive a signal indicatingthat the applicable range is exceeded from the electron gun controller15, and generate an alarm sound.

If the applicable range of the electron beam to be applied to theevaporation source 7 in the crucible 63 is exceeded, the electron guncontroller 15 can also perform an operation of stopping the operation ofthe electron gun power supply 10 for applying the high voltage to theelectron beam generator 61. This makes it possible to stop electron beamapplication and prevent damages to the crucible 63 and the like if theirradiation position of the electron beam to be applied to theevaporation source 7 in the crucible 63 has exceeded the applicablerange.

According to this embodiment, even when the apparatus controllerperforms the setting exceeding the electron beam applicable range, theelectron beam application range can be limited so as not to exceed theapplicable range determined by the electron gun controller 15. Since theelectron beam application range always exists inside the evaporationsource, the electron gun evaporation apparatus can be stably operated.

Also, a film formation method using the electron gun evaporationapparatus shown in FIG. 1 has an acquisition step of acquiringinformation concerning the irradiation position of the electron beamfrom the sweep controller 12, and information concerning the filmthickness growth rate corresponding to the irradiation position from thefilm thickness controller 13, an electron beam position control step ofdetermining an applicable range within which the electron beam can beapplied to the evaporation source, on the basis of the informationconcerning the irradiation position of the electron beam, and theinformation concerning the film thickness growth rate corresponding tothe irradiation position, and storing the applicable range in a memory,and an evaporation step of depositing an evaporated film on thesubstrate by applying the electron beam to the evaporation source andevaporating the evaporation source by heat, within the determinedapplicable range.

The preferred embodiment of the present invention has been explainedwith reference to the accompanying drawings. However, the presentinvention is not limited to the above embodiment and can be changed tovarious forms within the technical scope grasped from the description ofthe scope of the appended claims.

The present invention is not limited to the above embodiment and variouschanges and modifications can be made without departing from the spiritand scope of the invention. Therefore, to apprise the public of thescope of the present invention, the following claims are appended.

This application claims the benefit of Japanese Patent Application No.2007-018694, filed Jan. 30, 2007, which is hereby incorporated byreference herein in its entirety.

1. An electron gun evaporation apparatus including, in a vacuum chamberconfigured to be evacuated, an electron gun which generates an electronbeam by accelerating thermions generated from a filament by applying avoltage to the thermions, a film thickness controller which detects afilm thickness growth rate of an evaporated film formed on a substrateby applying the electron beam to an evaporation source and evaporatingthe evaporation source by heat, and a sweep controller which controls anirradiation position of the electron beam on the evaporation source,comprising: electron beam position control means for acquiringinformation concerning an irradiation position of the electron beam fromsaid sweep controller, and information concerning a film thicknessgrowth rate corresponding to the irradiation position from said filmthickness controller, determining an applicable range within which theelectron beam can be applied to the evaporation source, and storing theapplicable range.
 2. The electron gun evaporation apparatus according toclaim 1, wherein said electron beam position control means determines,as the applicable range, a range within which a distribution of the filmthickness growth rate is substantially constant in each scanningdirection of the electron beam, on the basis of the informationconcerning an irradiation position of the electron beam, and theinformation concerning a film thickness growth rate corresponding to theirradiation position.
 3. The electron gun evaporation apparatusaccording to claim 1, wherein if a predetermined electron beamapplication range has exceeded the applicable range determined by saidelectron beam position control means, said electron beam positioncontrol means controls application of the electron beam such that theapplicable range is not exceeded.
 4. The electron gun evaporationapparatus according to claim 3, wherein if the predetermined electronbeam application range has exceeded the applicable range, said electronbeam position control means performs at least one of an operation ofperforming notification by generating an alarm sound, and an operationof stopping an operation of an electron gun power supply which suppliesa high voltage to said electron gun.
 5. A film formation method using anelectron gun evaporation apparatus including, in a vacuum chamberconfigured to be evacuated, an electron gun which generates an electronbeam by accelerating thermions generated from a filament by applying avoltage to the thermions, a film thickness controller which detects afilm thickness growth rate of an evaporated film formed on a substrateby applying the electron beam to an evaporation source and evaporatingthe evaporation source by heat, and a sweep controller which controls anirradiation position of the electron beam on the evaporation source, thefilm formation method using the electron gun evaporation apparatuscomprises: an acquisition step of acquiring information concerning anirradiation position of the electron beam from the sweep controller, andinformation concerning a film thickness growth rate corresponding to theirradiation position from the film thickness controller; an electronbeam position control step of determining an applicable range withinwhich the electron beam can be applied to the evaporation source, on thebasis of the information concerning an irradiation position of theelectron beam acquired in the acquisition step, and the informationconcerning a film thickness growth rate corresponding to the irradiationposition, and storing the applicable range in a memory; and anevaporation step of depositing an evaporated film on the substrate byapplying the electron beam to the evaporation source and evaporating theevaporation source by heat, within the applicable range determined inthe electron beam position control step.
 6. The film formation methodusing the electron gun evaporation apparatus according to claim 5,wherein in the electron beam position control step, a range within whicha distribution of the film thickness growth rate is substantiallyconstant in each scanning direction of the electron beam is determinedas the applicable range, on the basis of the information concerning anirradiation position of the electron beam, and the informationconcerning a film thickness growth rate corresponding to the irradiationposition.